Method for cold rolling metals using an aqueous lubricant comprising at least a carboxylic acid, a phosphate ester and a wax

ABSTRACT

The invention concerns a method for cold rolling metals using an aqueous lubricant comprising: (1) at least a mixture based on at least an acid selected among saturated or unsaturated mono- or poly-carboxylic acids, comprising 5 to 40 carbon atoms; at least an acid phosphate ester of formula (RO)x—P(═O)(OH)x′, wherein: R is a hydrocarbon radical, optionally polyalkoxylated; x and x′ being equal to 3; the carboxylic acid and/or the acid phosphate ester being optionally neutralised by an organic or mineral base; and (2) at least a natural or synthetic wax exhibiting a melting point not less than 50° C. and having an average particle size ranging between 0.5 and 10 μm. The use of said lubricant enables to increase the productivity of the method by at least 15% relative to a method using a conventional lubricant.

[0001] The subject of the present invention is a cold rolling processfor metals using an aqueous lubricant comprising a mixture based on atleast one carboxylic acid, on at least one phosphate ester and includingat least one wax.

[0002] During metal deformation operations, especially such as coldrolling, it is necessary to use lubricants. This is because suchoperations take place at very high speeds, pressures and applied forces,the direct consequence of which is to create an extremely high frictioncoefficient. Such friction coefficient values limit the productivity ofthe machines, since their maximum capacity is rapidly reached.

[0003] There are various types of lubricants, such as for example wholeoils and aqueous lubricants.

[0004] In the particular case of cold rolling operations, the use ofwhole oils is the most common on an industrial scale, although the useof aqueous lubricants is mentioned in the literature. However, the useof these whole oils is limited and they do not allow the productivity ofthe process to be significantly increased. To reduce the thickness of asheet, for example, it is necessary to carry out several passes throughthe rolling mill. However, to increase productivity it would benecessary to be able to limit the number of passes through the rollingmill, which implies increasing the thickness reduction ratio of thesheet for each pass. To achieve such a result, the mechanical stresseswould have to be increased. But this would result in a degradation ofthe surface finish of the rolled sheet (scratches) and/or in the maximumreduction capacity of the tool being exceeded.

[0005] The use of what are called “extreme pressure” additives delaysthe appearance of these phenomena. Thus, the extreme-pressure propertiesof the lubricant allow the deformation of the metal (thicknessreduction) to be increased while remaining below the limiting reductionforce of the machine, by limiting microwelds between the surfaceasperities on the metal and on the tool.

[0006] Various types of extreme-pressure additives exist, the fields ofapplication of which are different depending, among other things, on thetemperatures at the points of contact between the tool and the metal tobe converted. The reason for this is that these additives above acertain temperature release a compound that reacts with the metalsurface to create a species that will protect the system. On the otherhand, the field of use of the additive in question will be limited bythe temperature at which the species created will degrade. Thus, whenchlorinated compounds are used as extreme-pressure additive, a metalchloride layer is created on the surface of the metal by reaction of thechlorine released with said surface at an appropriate temperature. Theother additives used are based on sulfur (sulfur-containing esters,sulfur-containing oils) or based on phosphorus (phosphate esters) ormixtures thereof. They result in the formation of a metal sulfide or ametal phosphate.

[0007] However, the use of such additives does not always provide asatisfactory solution for increasing the productivity.

[0008] As regards the use of an aqueous lubricant in cold rolling, thishas no particular advantage, except that it does mean that the metal andthe tool are cooled more effectively. However, it is possible toincrease the thickness reduction ratio per pass of the sheet by addingconventional extreme-pressure additives. Unfortunately, these aqueouslubricants are very far from providing a satisfactory solution forachieving the desired productivity increase. In addition, the occurrenceof a phenomenon unacceptable in the field, namely an irreversibledegradation of the metal surface (coloration, roughness), may beobserved.

[0009] Thus, as may be stated in the case of the cold rolling of metals,there are still no lubricants that make it possible to reduce the numberof passes through the rolling mill and allow the productivity of thisprocess to be increased without substantial degradation of the surfacefinish of the rolled product being observed.

[0010] The object of the present invention is to propose a cold rollingprocess for metals that does not have the drawbacks of the usualprocesses. Thus, the process according to the invention makes itpossible to work under very severe conditions, representative ofhigh-productivity conditions, while still maintaining the surface finish(coloration, brightness) of the deformed metal.

[0011] These and other objectives are achieved by the present invention,the subject of which is thus a cold rolling process for metals using anaqueous lubricant comprising (1) at least one mixture based on at leastone acid chosen from saturated or unsaturated, monocarboxylic orpolycarboxylic acids containing 5 to 40 carbon atoms; on at least oneacid phosphate ester of formula (RO)_(x)—P(═O) (OH)_(x′), in whichformula R is an optionally polyalkoxylated hydrocarbon radical, x and x′being equal to 1 or 2, provided that the sum of x and x′ is equal to 3;the carboxylic acid and/or the acid phosphate ester being optionallyneutralized by an organic or mineral base; and (2) at least one naturalor synthetic wax having a melting point not less than 50° C. and havinga mean particle size ranging between 0.5-10 μm.

[0012] Unless otherwise indicated, the size measurements are carried outeither by laser diffraction or by light scattering. There is nodifficulty for those skilled in the art to choose one of these twomethods depending on the size of the objects.

[0013] The expression “conventional lubricant” is understood to meaneither a whole oil containing one or more extreme-pressure additives, oran aqueous lubricant also containing one or more extreme-pressureadditives. It should be noted that conventional extreme-pressureadditives are compounds containing phosphorus (such as for examplephosphates) or sulfur (such as especially sulfonates).

[0014] Completely surprisingly, the use of an aqueous lubricantaccording to the invention allows the productivity of cold rollingoperations to be significantly improved. Thus, by using this lubricantit is possible to increase the thickness reduction ratio of the rolledmetal by at least 15%, more particularly by at least 20% and highlyadvantageously by at least 30%, compared with the maximum reductionratio achievable by a rolling mill using a conventional lubricant,whether a whole oil containing one or more extreme-pressure additives oran aqueous lubricant containing one or more extreme-pressure additives.

[0015] Moreover, such results are achieved while maintaining a surfacefinish of the rolled metal that meets the requirements of those skilledin the art, especially as regards its coloration and its brightness.

[0016] Finally, the lubricants employed within the context of thepresent invention, after thermal degradation once the rolling operationhas been carried out, leave no solid residues on the metal.

[0017] However, other advantages and features will become more clearlyapparent on reading the description and from the examples that follow.

[0018] Thus, as was indicated previously, the aqueous lubricantcomprises at least one mixture based on at least one acid chosen fromsaturated or unsaturated, monocarboxylic or polycarboxylic acidscontaining 5 to 40 carbon atoms; on at least one acid phosphate ester offormula (RO)_(x)—P(═O) (OH)_(x′), in which formula R is an optionallypolyalkoxylated hydrocarbon radical, x and x′ being equal to 1 or 2,provided that the sum of x and x′ is equal to 3, the carboxylic acidand/or the acid phosphate ester being optionally neutralized by anorganic or mineral base.

[0019] It should be noted that the mixture (1) may be an aqueoussolution or an aqueous dispersion. The term “dispersion” denotes adispersion of vesicles, droplets or micelles in an aqueous medium.

[0020] Firstly, the carboxylic acid used possesses one or morecarboxylic functional groups and at least one radical containing 5 to 40carbon atoms, said radical being a linear or branched, alkyl or alkenylradical having one or more ethylenically unsaturated groups(carbon-carbon double bonds) and optionally being substituted with oneor more hydroxyl radicals.

[0021] According to one advantageous method of implementing theinvention, the acid possesses one or more carboxylic functional groupsand a radical containing 7 to 30 carbon atoms, optionally substitutedwith one or more hydroxyl radicals and optionally having one or moreethylenically unsaturated groups.

[0022] Preferably, said acid possesses one carboxylic functional groupor two. When this second functional group is present, it may or may notbe at the end of the chain.

[0023] Preferably, the carboxylic acid is a saturated or unsaturatedfatty acid, more particularly comprising a single carboxylic functionalgroup, or a mixture of several fatty acids.

[0024] As examples of saturated fatty acids, mention may be made ofcaproic, caprylic, capric, lauric, myristic, stearic, isostearic,palmitic, behenic and lignoceric acids.

[0025] As examples of unsaturated fatty acids, mention may be made ofthe unsaturated fatty acids having a single ethylenically unsaturatedgroup, such as linderic, myristoleic, palmitoleic, oleic and erucicacids; unsaturated fatty acids having two ethylenically unsaturatedgroups, such as linoleic acid; unsaturated fatty acids having threeethylenically unsaturated groups, such as linolenic acid; andunsaturated fatty acids carrying a hydroxyl group, such as ricinoleicacid, as well as mixtures thereof.

[0026] It is preferred to use palmitic, behenic, stearic, isostearic,palmitoleic, oleic, erucic, linoleic, linolenic or ricinoleic acids, ormixtures thereof.

[0027] As regards the acid phosphate esters, these correspond to thefollowing formula (RO)_(x)—P(═O) (OH)_(x′), in which formula theradicals R, which may or may not be identical, represent an optionallypolyalkoxylated hydrocarbon radical, x and x′ being equal to 1 or 2,provided that the sum of x and x′ is equal to 3.

[0028] Preferably, the acid phosphate ester corresponds to the followingformula: [R(OA)_(y)]_(x)—P(═O) (OH)_(x), in which formula the radicalsR, which may or may not be identical, represent a hydrocarbon radicalcontaining 1 to 30 carbon atoms, the radicals A, which may or may not beidentical, represent a linear or branched alkylene radical containing 2to 4 carbon atoms, y, which is an average value, is between 0 and 100and x and x′ are equal to 1 or 2, provided that x+x′=3.

[0029] More particularly, R is a hydrocarbon radical containing 1 to 30carbon atoms, said radical being a saturated or unsaturated, aliphaticor cycloaliphatic radical or an aromatic radical. Preferably, theradicals R, which are identical or different, are linear or branchedradicals containing 8 to 26 carbon atoms, these being alkyl radicals oralkenyl radicals carrying one or more ethylenically unsaturated groups.As examples of such radicals, mention may especially be made of stearyl,oleyl, linoleyl and linolenyl radicals. Furthermore, the radicals R,which may or may not be identical, may be aromatic radicals carryingalkyl, arylalkyl or alkylaryl substituents, these radicals containing 6to 30 carbon atoms. As examples of such radicals, mention may be made,among others, of nonylphenyl, monostyrylphenyl, distyrylphenyl andtristyrylphenyl radicals.

[0030] More particularly, the OA groups, which may or may not beidentical, correspond to an oxyethylene, oxypropylene or oxybutyleneradical, or mixtures thereof. Preferably, said group corresponds to anoxyethylene and/or oxypropylene radical.

[0031] As regards the average value of y, this is preferably between 0and 80.

[0032] The acid phosphate ester forming part of the composition of themixture (1) may be formed from a combination of several of them.

[0033] Furthermore, the carboxylic acid and/or the acid phosphate estermay be in a form neutralized by a mineral or organic base.

[0034] It should be noted that the bases used are preferablywater-soluble. The term “water-soluble bases” is understood to meancompounds soluble in an aqueous medium, at 20° C., with a concentrationof from 3 to 7% by weight.

[0035] Thus, as nonlimiting examples of such compounds, mention may bemade of alkali-metal and ammonium hydroxides, hydroxycarbonates,carbonates and bicarbonates.

[0036] Preferably, the bases employed are organic bases but are moreparticularly chosen from primary, secondary or tertiary amines orpolyamines comprising at least one linear, branched or cyclichydrocarbon radical having 1 to 40 carbon atoms, said radical beingoptionally substituted with one or more hydroxyl radicals and/or one ormore alkoxylated groups. The said alkoxylated groups are preferablyethoxylated units. In addition, the number of alkoxylated units, ifpresent, is less than or equal to 100.

[0037] According to a preferred method of implementation of theinvention, when the amines have at least two amine functional groups,said functional groups are separated in pairs by a number of carbonatoms ranging between 2 and 5.

[0038] As suitable amines, mention may be made of monoethanolamine,diethanolamine, ethylenediamine, aminoethylethanolamine andaminomethylpropanolamine. Polyalkoxylated fatty amines may also be usedas organic base, such as for example those sold by Rhodia Chimie underthe name RHODAMEEN® CS20.

[0039] Advantageously, at least the carboxylic acid is neutralized by anorganic base, the amount of the latter being such that the total numberof moles of amine functional groups is at least equal to the totalnumber of moles of carboxylic acid functional groups, and preferably atleast twice as large.

[0040] The mixture (1) may optionally furthermore include at least onenonionic surfactant. The use of this type of compound may be desiredwhen the mixture (1) is in the form of a dispersion.

[0041] Among suitable surfactants of this type, mention may be madeinter alia of:

[0042] polyalkoxylated alkylphenols, in particular those in which thealkyl substituent is a C₆-C₁₂ one;

[0043] polyalkoxylated mono-, di- or tri-(alkylaryl)phenol, preferablychosen from those in which the alkyl substituent is a C₁-C₆ one;

[0044] polyalkoxylated aliphatics, more particularly C₈-C₂₂ alcohols;

[0045] polyalkoxylated triglycerides;

[0046] polyalkoxylated fatty acids;

[0047] polyalkoxylated sorbitan esters; and

[0048] optionally polyalkoxylated, preferably C₈-C₂₀, fatty acid amides.

[0049] The number of polyalkoxylated units, if present, of thesenonionic surfactants usually varies from 2 to 100. It should be notedthat the term “polyalkoxylated units” is understood to mean ethoxylatedunits, propoxylated units or mixtures thereof.

[0050] The amount of surfactant usually varies, if it is present,between 1 and 30% by total weight of the mixture (1).

[0051] In the mixture (1), the contents of carboxylic acid, of acidphosphate ester, optionally of base, preferably an organic base, andoptionally of nonionic surfactant are such that the solids content ofthe aqueous medium is at least 10% by weight. More precisely, the solidscontent is between 10 and 70% by weight. Preferably, the solids contentvaries between 10 and 40% by weight.

[0052] Advantageously, the pH of the mixture (1) ranges between 7 and 9.This pH range may inter alia be achieved by the addition of a bufferagent to said mixture.

[0053] According to a variant of the invention, said mixture (1) iscombined with at least one metal in the form of a multivalent ion. Moreparticularly, said metal may be in the form of a divalent ion or atrivalent ion. Likewise, it would not be excluded to use several metals,in identical or different oxidation states.

[0054] According to one particular method of implementing the invention,said metal is chosen from columns IIA, VIII, IB, IIB and VIB, with theexception of cobalt and nickel.

[0055] More particularly, the metals are chosen from calcium, magnesium,copper, zinc, iron, aluminum and chromium, by themselves or as mixtures.

[0056] In the case of this variant, the mixture (1) associated with themetal is more precisely in the form of a dispersion comprising lamellarcrystallites having a length ranging between 0.1 and 100 μm, a widthranging between 0.5 and 30 μm and a thickness ranging between 5 and 200nm.

[0057] These crystallites comprise a stack of organic phases (O) and ofaqueous solutions (A) in the sequence O/[A/O]n, n being an integerdifferent from 0 and such that a stack has a thickness of 5 to 200 nm.More particularly, n is between 1 and 20.

[0058] As regards the size of the crystallites, their length isadvantageously between 0.5 and 20 μm. The width of the lamellarcrystallites is more particularly between 0.5 and 10 μm. Finally, thethickness of the lamellar crystallites is preferably between 10 and 100nm. The abovementioned dimensions of the lamellar crystallitescorrespond to average values. In other words, there is a distribution inthe sizes of the lamellar crystallites, the average of which lies withinthe above ranges. The measurements of the dimensions of the lamellarcrystallites are carried out using transmission electron microscopy on aspecimen vitrified cryogenically (Cryo-Met—see O. Aguerre-Chariol, M.Deruelle, T. Boukhnikachvili, M. In and N. Shahidzadeh, “Cryo-Met suréchantillons vitrifiés: principes, applications aux émulsions etdispersions de tensioactifs” [“Cryo-Met on vitrified specimens:principles and applications to surfactant emulsions and dispersions”,Proceedings of the Congrés Mondial de l'Emulsion [(World EmulsionCongress], Bordeaux, France (1997)).

[0059] Within the context of this variant, the crystallites areadvantageously used in the presence of at least one nonionic surfactant.

[0060] The crystallites may be obtained by bringing a solution ordispersion containing the acid phosphate ester and the optionallyneutralized carboxylic acid into contact with the metal in ionic and/ormetallic form.

[0061] As regards the metal, this may equally well be in its metallicform or in the form of a multivalent cation. Said cation may itself bein the form of a solid, a solution or a dispersion.

[0062] When the metal is used in the form of a solution, preferably anaqueous solution, it is possible to use, for example, salts of mineralacids, such as halides, with chlorides for example, or nitrates; andlikewise salts or organic acids, such as, among others, formates andacetates.

[0063] It is also conceivable to use the metal in an oxide, hydroxide orcarbonate form, or the metal itself.

[0064] Preferably, the contacting is carried out in the presence of atleast one compound having the effect of buffering the pH. Moreparticularly, one or more compounds are chosen such that the pH of themedium is between 7 and 9.

[0065] The contacting takes place with stirring. Preferably, the metalin the chosen form is introduced into the mixture (1), the carboxylicacid preferably being neutralized by an organic base.

[0066] The operation advantageously takes place at a temperature below100° C. and preferably at a temperature ranging between 20 and 60° C.

[0067] The aqueous lubricant used in the cold rolling process accordingto the invention furthermore includes at least one natural or syntheticwax, having a melting point not less than 50° C. and having a meanparticle size ranging between 0.5-10 μm.

[0068] The wax or waxes are dispersed within the mixture (1) in ahomogeneous and stable manner.

[0069] More particularly, these waxes are chosen from natural waxes ofthe type consisting of paraffin waxes or synthetic waxes having esterand/or amide functional groups.

[0070] Preferably, the waxes used are those having amide functionalgroups. Said waxes may be obtained, for example, by a condensationreaction, and more particularly by a reaction of an ester or acidfunctional group with an amine functional group. Preferably, these waxeshave a degree of polymerization of at most 10 and advantageously at most3.

[0071] According to a preferred method of implementing the invention,the aforementioned waxes correspond to the following formula:R′—CO-A-(CR″₂)_(n″)A-CO′R′, in which formula the radicals R′, which mayor may not be identical, represent an aliphatic radical containing 5 to22 carbon atoms, said radical being saturated or having one or moreconjugated or nonconjugated carbon-carbon double bonds; the radicals R″,which may or may not be identical, represent a hydrogen atom or an alkylradical containing 1 to 4 carbon atoms; n represents an integer between2 and 12; and the radicals A, which may or may not be identical,represent —O— or —NH—. It should be noted that the radicals A arepreferably of the same type.

[0072] As examples of such waxes, mention may most particularly be madeof bis(amide) waxes, such as an ethylene bis(alkylamide) or an ethylenebis(alkenylamide).

[0073] Preferably, the melting point of the waxes is not less than 80°C.

[0074] The wax content in the aqueous lubricant during its use isbetween 0.05 and 10% by weight of the lubricant, preferably between 0.05and 5% by weight of the lubricant.

[0075] The wax may be introduced into the mixture either byincorporating the wax particles, the size of which lies within theabovementioned range, into said mixture. It is also possible tointroduce the wax by adding the latter in molten form to the mixture,and to precipitate it in the mixture, the operation advantageouslytaking place by carrying out a grinding operation so as to obtain theappropriate size of particles.

[0076] The aqueous lubricants according to the invention may alsoinclude additives that are conventional in this field, such aspreservatives, anticorrosion agents, antifoams and stabilizers.

[0077] It would not be outside the scope of the present invention to addconventional lubrication additives to the aqueous lubricant used in theinvention. As nonlimiting examples of such additives, mention may bemade of mineral or vegetable oils, fatty alcohols, fatty acids and theirester or amide derivatives. The content of these compounds, if present,in the aqueous lubricant during its use does not usually exceed 10% byweight of the aqueous lubricant during its use.

[0078] The lubricants that have just been described are particularlyappropriate for lubrication in the cold rolling of metals.

[0079] The metals on which such treatments may be carried out areespecially, and mainly, steels, stainless steels, aluminum, copper,zinc, tin, copper-based alloys (bronze, brass), etc.

[0080] The present invention is most particularly applicable to the coldrolling of stainless steel.

[0081] A specific but nonlimiting example of the invention will now bepresented.

EXAMPLE Composition According to the Invention

[0082] The following mixture was prepared in water, and with stirring:oleic acid: 9% by weight wax (*): 10% by weight RHODAFAC PA35 (**): 5%by weight H₃PO₄/diethanolamine: sufficiant amount to have a pH ofbetween 7 and 9 (buffer).

[0083] The resulting mixture was then diluted 10 times.

Tests

[0084] The tests took place on a rolling mill comprising two 10 cmdiameter rolls.

[0085] The rolled metal was coiled stainless steel, 10 mm in width andabout 0.4 mm in thickness.

[0086] The applied force on the rolls varied from 200 metric tonnes/m to1200 metric tonnes/m, so as to obtain a sheet reduction ratio varyingfrom 20 to 55%.

[0087] During the tests, the lubricant was used at 80° C.

Results

[0088] The lubricant according to the invention made it possible toobtain, for a linear speed of the rolls of 5 m/s, reduction ratios of atleast 55% without having reached the clamping limit of the rolling mill.

[0089] The same tests carried out with a lubricant of the whole oiltype, containing an extreme-pressure additive (of the phosphate estertype), showed that, for a linear speed of 5 m/s, a maximum reductionratio of 30% was obtained before clamping of the rolling mill.

[0090] The use of an aqueous lubricant containing a phosphate ester asextreme-pressure additive showed that the maximum reduction ratioachieved before clamping of the rolling mill was 45%.

[0091] It should be noted that increasing the linear speed (12 m/sspeed) confirmed the superiority of the performance of the lubricantsaccording to the invention compared with whole oils and with aqueouslubricants.

1. A cold rolling process for metals using an aqueous lubricantcomprising (1) at least one mixture based on at least one acid chosenfrom saturated or unsaturated, monocarboxylic or polycarboxylic acidscontaining 5 to 40 carbon atoms; on at least one acid phosphate ester offormula (RO)_(x)—P(═O) (OH)_(x′), in which formula R is an optionallypolyalkoxylated hydrocarbon radical, x and x′ being equal to 1 or 2,provided that the sum of x and x′ is equal to 3; the carboxylic acidand/or the acid phosphate ester being optionally neutralized by anorganic or mineral base; and (2) at least one natural or synthetic waxhaving a melting point not less than 50° C. and having a mean particlesize ranging between 0.5-10 μm.
 2. The process as claimed in one of thepreceding claims, characterized in that the carboxylic acid of themixture (1) comprises one or more carboxylic functional groups and atleast one linear or branched, alkyl radical or alkenyl radical havingone or more ethylenically unsaturated groups, said radicals optionallybeing substituted with one or more hydroxyl radicals.
 3. The process asclaimed in one of the preceding claims, characterized in that the acidphosphate ester of the mixture (1) corresponds to the following formula:[R(OA)_(y)]_(x)—P(═O) (OH)_(x′), in which formula the radicals R, whichmay or may not be identical, represent a hydrocarbon radical containing1 to 30 carbon atoms, the radicals A, which may or may not be identical,represent a linear or branched alkylene radical containing 2 to 4 carbonatoms, y, which is an average value, is between 0 and 100 and x and x′are equal to 1 or 2, provided that x+x′=3.
 4. The process as claimed inone of the preceding claims, characterized in that the mineral baseamong the basic compounds creating monovalent species, chosen amongalkali-metal and ammonium hydroxides, hydroxycarbonates, carbonates andbicarbonates.
 5. The process as claimed in one of the preceding claims,characterized in that the organic base is chosen from primary, secondaryor tertiary amines or polyamines, comprising at least one linear,branched or cyclic hydrocarbon radical having 1 to 40 carbon atoms,optionally substituted with one or more hydroxyl radicals and/or one ormore oxyalkylene groups.
 6. The process as claimed in one of thepreceding claims, characterized in that the waxes are natural waxeschosen from paraffin waxes, synthetic waxes comprising ester and/oramide functional groups.
 7. The process as claimed in the precedingclaim, characterized in that the synthetic waxes correspond to thefollowing formula: R′—CO-A-(CR″₂)_(n)-A-CO—R′, in which formula theradicals R′, which may or may not be identical, represent an aliphaticradical containing 5 to 22 carbon atoms, said radical being saturated orhaving one or more conjugated or nonconjugated carbon-carbon doublebonds; the radicals R″, which may or may not be identical, represent ahydrogen atom or an alkyl radical containing 1 to 4 carbon atoms; nrepresents an integer between 2 and 12; and the radicals A, which may ormay not be identical, represent —O— or —NH—.
 8. The process as claimedin either of claims 6 and 7, characterized in that the waxes have amelting point not less than 80° C.
 9. The process as claimed in one ofthe preceding claims, characterized in that the mixture (1) comprises atleast one metal in the form of a multivalent ion; the assembly being inthe form of lamellar crystallites of length ranging between 0.1 and 100μm, of width ranging between 0.5 and 30 μm and of thickness rangingbetween 5 and 200 nm, comprising a stack of organic phases (O) and ofaqueous solutions (A) in the sequence O/[A/O]n, n being an integerdifferent from 0 and such that the stack has a thickness of 5 to 200 nm,the organic phases comprising the mixture (1) and said metal.
 10. Theprocess as claimed in the preceding claim, characterized in that thelength of the lamellar crystallites is between 0.5 and 20 μm, the widthof the lamellar crystallites is between 0.5 and 10 μm and the thicknessof the lamellar crystallites is between 10 and 100 nm.
 11. The processas claimed in the preceding claim, characterized in that the metal is inthe form of a multivalent cation chosen from columns IIA, VIII, IB, IIBand VIB, with the exception of cobalt and nickel, by themselves or asmixtures.
 12. The process as claimed in one of the preceding claims,characterized in that the total content of compounds (1) and (2) in theaqueous lubricant during its use is between 0.05 and 10% by weight ofthe lubricant, preferably between 0.05 and 5% by weight of thelubricant.
 13. The process as claimed in one of the preceding claims,characterized in that it is applicable to the cold rolling of metalssuch as steels, stainless steels, copper, zinc, tin and copper-basedalloys (bronze, brass).
 14. The process as claimed in the precedingclaim, characterized in that it is applicable to the cold rolling ofstainless steel.